Analysis of the transport of amino acids in the ocular lens is continuing. Our main objective currently is to complete a comparison of transport at the anterior and posterior faces of the lens. Since the tissue consists of a homogeneous population of cells - an anterior epithelium, and differentiated fiber cells, arising from and uncontaminated by the epithelium, at the posterior surface - an opportunity is presented to assess the effect of differentiation by measuring transport at either surface. This is done by positioning the lens on top of vials filled with a stirred Ringer-bicarbonate solution containing the test-substance. Using this technique, we have obtained evidence for the presence in the bovine lens of the A-, ASC-, L-, Ly positive and GLY-systems of transport of Christensen and Vidaver, and are identifying selective changes in transport resulting from differentiation. We are determining the effect of aging on transport at the two poles of the bovine lens. As well as completing a study of amino acids, we intend to examine transport of sugars and substituents of nucleic acids ("nucleics") in the calf, steer and bull lens. Kinetic analyses in the presence of appropriate inhibitors are to be performed on the "nucleics" in order to better define the systems of transport which are present in studies of the completely immersed calf lens.